The heart is the center of circulatory system of an individual. The left portions of the heart draw oxygenated blood from lungs and pump the blood to body organs to provide the organs with their metabolic needs for oxygen. The right portions of the heart draw deoxygenated blood from the organs and pump the blood to the lungs where the blood gets oxygenated.
In a normal heart, the sinuatrial node (SA node), located in high right atrium (HRA), generates electrical impulses that propagate to cardiac muscle (myocardium), thereby stimulating the cardiac muscle. The SA node has specialized cells that undergo spontaneous generation of action potentials at a rate of 100-110 action potentials (“beats”) per minute, causing generation of electrical impulses. The ordered stimulation of the cardiac muscle allows efficient contraction of the heart, thereby allowing blood to be pumped throughout the body.
The sinus rhythm normally controls both atrial and ventricular rhythm. When functioning properly, electrical impulses are spontaneously generated by the SA node. Electrical impulse is propagated through the right atrium and through Bachmann's bundle to left atrium, thereby stimulating the cardiac muscle of the atria to contract. The conduction of the electrical impulse throughout the atria is seen on Electrocardiogram (ECG) of the heart as the P wave.
As the electrical impulse spreads throughout the atria, the electrical impulse travels from the SA node to Atrio-Ventricular (A-V) node, which electrically connects atrial and ventricular chambers via specialized pathways, known as internodal tracts. The A-V node delays the electrical impulse on the impulse's way to the ventricle, giving the atria time to contract first. Without the delay, the atria and ventricles would contract at the same time, and blood wouldn't flow effectively from the atria to the ventricles. The electrical impulse then enters the base of the ventricle at bundle of His and follows left and right bundle branches. The electrical impulse travels at the high velocity through Purkinje fibers at the end of the branches into the ventricles, causing stimulation of the cardiac muscle of the ventricles. The stimulation of the cardiac muscle causes the right and left ventricles to contract. The conduction of the electrical impulse through the ventricular cardiac muscles produces the QRS complex on the ECG. Thus, normal cardiac rhythm is controlled by the pacemaker activity of the SA node and the delay in the AV node.
Abnormal cardiac rhythms may occur in individuals due to improper conduction of electrical impulse through the A-V node. For example, the improper conduction of the electrical impulse is encountered due to leakage of the electrical impulse while passing through the A-V node. Typically, conduction of the electrical impulse through the A-V node is analyzed using an atrial stimulation technique. In the atrial stimulation technique, High Right Atrium (HRA) is simulated using a plurality of stimulation events. During each stimulation event, the HRA is stimulated with a series of pulses with equal pacing cycle length followed by an extra-stimulus pulse having different pacing cycle length using a pacing electrode (also known as lead). It can be noted that pacing cycle length of the extra-stimulus pulse is reduced by a pre-determined value during subsequent stimulation events.
For each stimulation event, a waveform that indicates atrial contraction and traversal of electrical impulse through the A-V node is recorded. Then, the Atrium-Hision (A-H) interval, which is a time interval between atrial contraction and traversal of the electrical impulse through the A-V node upon applying the extra-stimulus pulse, is measured for each stimulation event. Presently, the A-H interval is measured manually by placing horizontal calipers on the waveform. This may be a time consuming affair and lead to inaccurate measurement of A-H intervals. Moreover, a physician may manually determine whether A-H jump is present by comparing A-H intervals corresponding to consecutive stimulation events. For example, the physician may determine that the A-H jump is present if the difference in the A-H intervals is greater than 50 ms. Due to inaccurate A-H intervals, the physician may not be able to precisely detect presence of A-H jump. It is also cumbersome to detect A-H jump as a physician needs to iteratively carry out stimulation events until an A-H jump is detected or satisfactory results are obtained.